It is now a common knowledge that liquid products of dyes are generally advantageous in using as compared with powder products of dyes in many respects, but various difficulties are entailed to obtain the liquid products of dyes. Here, essential requisites required for such liquid-state product are that it contains a substantial content of a dye, namely the dye is of a sufficiently high concentration and that the liquid dye product is stable for a long period of time against the change of the atmospheric temperature, etc. with time and maintains its homogeneity.
Heretofore, various methods have been proposed to prepare liquid-state compositions of anionic dyes, among which direct dyes, particularly, black dyes have generally a low water-solubility. Furthermore, liquid compositions of the black dyes are, when preserved for a long period of time, degraded owing to oxidation, etc. ascribed to the amino group the black dyes have in their molecular structures, and run into undesirable results such as increase in viscosity, lowering in concentration, production of precipitates, etc.